1. Field of the Invention
The present invention relates to a turbo compressor capable of compressing a liquid by a plurality of impellers, and a refrigerator including the turbo compressor.
Priority is claimed on Japanese Patent Application No. 2008-027071, filed Feb. 6, 2008, the content of which are incorporated herein by reference.
2. Description of the Related Art
As refrigerators which cool or freeze objects to be cooled, such as water, a turbo refrigerator or the like including a turbo compressor which compresses and discharges a refrigerant by impellers is known.
In a compressor, when a compression ratio increases, the discharge temperature of the compressor becomes high and the volumetric efficiency thereof degrades. Thus, in the turbo compressor included in the above-mentioned turbo refrigerator or the like, a refrigerant may be compressed in a plurality of stages. For example, a turbo compressor which includes two compression stages provided with an impeller and a diffuser and compresses a refrigerant sequentially in these compression stages is disclosed in Japanese Patent Unexamined Application, First Publication No. 2007-177695.
Meanwhile, in this type of turbo compressor, a liquid pool may be formed at a bottom of a flow path through which a refrigerant gas or the like circulates, as the refrigerant gas filled into the turbo compressor during standby of the turbo refrigerator is liquefied depending on the conditions of outside air temperature. When the turbo refrigerator is started in this state, the liquid is sucked by the turbo compressor and collides against the impeller. As a result, an excessive power load acts on the impeller. Fatigue breaking of the impeller by liquid colliding may occur by repeating such starting and standby of such a turbo refrigerator. Additionally, even if the impeller does not lead to breaking, problems may occur such as the surface roughness of impeller vanes degrading by the collision of the liquid, and the compression performance degrades.